Backing up “mercurial” Photos data is only half the problem. The tricky part is restoring it in a way Photos actually recognizes as equivalent to the original library state. Photos Backup Anywhere restore works by re-importing items while explicitly reapplying Photos-level attributes: paired assets for Live Photos, burst membership and picks, slo-mo metadata, edits, locations, adjusted capture dates, and then reconstructing albums after the items exist again in the library.

In other words, the filesystem copy isn’t treated as the source of truth. The restore verifies items against what was backed up and only then rebuilds higher-level structure like albums. That’s the piece I didn’t see addressed elsewhere, and what originally motivated me to build it.